Ultrasonic transmission devices are frequently used in a variety of applications, such as, for example, surgical operations and procedures. Ultrasonic surgical devices usually include a transducer assembly that converts electrical energy into vibrational motion at ultrasonic frequencies. The vibrational motion of the transducer assembly is transmitted to vibrate a distal end of a transmission component. The distal end of the transmission component, may transmit the ultrasonic energy to selected tissue of a patient, for example, to cut, dissect, and cauterize the tissue.
The ultrasonic vibration is induced in the transmission component by exciting one or more piezoelectric elements of the transducer assembly by an electrical signal. The electrical signal is transmitted to electrodes that are coupled to the piezoelectric elements. The electrodes are typically disposed on each side of the piezoelectric elements. When the electrical signal is transmitted to the electrodes, an electric field is established across the piezoelectric elements causing the piezoelectric elements to generate a mechanical standing wave at a frequency approximately equal to the frequency of the electrical excitation signal.
One of the problems associated with ultrasonic surgical instruments is uncontrolled and undampened vibrations of the transmission component as well as material fatigue resulting therefrom. Conventional mechanical dampening has been used to reduce undesired vibrations of transmission components of ultrasonic surgical instruments. For example, silicone rings have been disposed near nodes of the transmission component to reduce undesired vibration. However, the silicone rings can decrease the performance of the transmission component, dissipate desirable ultrasonic energy, increase the design time of the transmission component, and increase the heating of the transmission component. In addition, the distribution of current flow through the transducer assembly cannot be sensed or controlled.
Accordingly, there is a need for improved devices and methods to control the vibration of ultrasonic transmission components to allow the desired frequency to pass to the distal end of the transmission components. It would also be desirable to dampen the undesired vibration of the vibrational elements of the transducer assembly.